exofs: Optimize read_4_write

Don't attempt a read passed i_size, just zero the page and be
done with it.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index a755523..c8f58a9 100644 (file)
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -350,8 +350,10 @@ static int readpage_strip(void *data, struct page *page)
 
                if (!pcol->read_4_write)
                        unlock_page(page);
-               EXOFS_DBGMSG("readpage_strip(0x%lx, 0x%lx) empty page,"
-                            " splitting\n", inode->i_ino, page->index);
+               EXOFS_DBGMSG("readpage_strip(0x%lx) empty page len=%zx "
+                            "read_4_write=%d index=0x%lx end_index=0x%lx "
+                            "splitting\n", inode->i_ino, len,
+                            pcol->read_4_write, page->index, end_index);
 
                return read_exec(pcol);
        }
@@ -722,11 +724,28 @@ int exofs_write_begin(struct file *file, struct address_space *mapping,
 
         /* read modify write */
        if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
+               loff_t i_size = i_size_read(mapping->host);
+               pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
+               size_t rlen;
+
+               if (page->index < end_index)
+                       rlen = PAGE_CACHE_SIZE;
+               else if (page->index == end_index)
+                       rlen = i_size & ~PAGE_CACHE_MASK;
+               else
+                       rlen = 0;
+
+               if (!rlen) {
+                       clear_highpage(page);
+                       SetPageUptodate(page);
+                       goto out;
+               }
+
                ret = _readpage(page, true);
                if (ret) {
                        /*SetPageError was done by _readpage. Is it ok?*/
                        unlock_page(page);
-                       EXOFS_DBGMSG("__readpage_filler failed\n");
+                       EXOFS_DBGMSG("__readpage failed\n");
                }
        }
 out: